Field of the Invention
The invention relates to a magnetic resonance apparatus with a computer that is designed to emit, on each of at least one control channel, at least one control signal, generated from a sequence of values to control, via each channel, least one component of the magnetic resonance device.
Description of the Prior Art
For control and measurement tasks in magnetic resonance devices, complex control devices are used, including a computer to provide a user interface and for data management and likewise to carry out offline computing operations, which computer in turn controls a plurality of further intelligent computing units, which include processors, FPGAs or ASICs and carry out application-specific calculations in hard real-time. These further intelligent computing devices are designed as PC plug-in cards or as separate modules.
The further intelligent computing devices are used in particular for timely control of gradient currents and to provide a frequency-determining synthesizer and a frequency-determining oscillator to generate excitation pulses. The further computing devices additionally include processors to process a data stream from analog-digital converters, in particular for processing the magnetic resonance measurement signals.
Control of the gradient currents is achieved inter alia by calculating gradient anchor points for the x-, y- and z-axes, calculating gradient-based compensation methods, such as digital eddy current compensation, and calculating an axis-specific compensation for time-lags in the gradients. The processing of the ADC data stream of the measured values also includes numerous computation-intensive tasks, in particular the frequency conversion of the measured data using NCO (numerically controlled oscillator) output signals, filtering and reducing the sampling rate for the measured data, sorting the ADC data according to measurement channels, and providing the ADC data to the computer.
The combination of requirements for a hard real-time, that is, the requirement for reaction times of the further computing devices, which are shorter than half the sampling interval, preferably for generating distortion-free signals that are clearly further below that level, with the high computation requirements of individual tasks requires computing-intensive and hence very expensive further computing devices. Due to the requirement for real-time, it is not possible to use conventional programmable computers for these tasks, since even when real-time operating systems are used, the hard real-time required is not achieved.